Home network system and method

ABSTRACT

A home network, in one embodiment including a home wiring system; a demarcation point unit in electrical communication with the home wiring system; and a home network module in electrical communication with the home wiring system. The home network module is adapted for connection to a home electronic device. The demarcation point unit passes data to and receives data from the home electronic device through the home network module.

RELATED APPLICATIONS

[0001] This application claims the benefit of the filing date ofco-pending U.S. Provisional Application, Serial No. 60/229,263, filedAug. 30, 2000, entitled “Home Network Method And Apparatus,” andProvisional Application, Serial No. 60/230,110, filed Sep. 5, 2000,entitled “Home Network Method And Apparatus,” the entirety of whichprovisional applications is incorporated by reference herein.

FIELD OF THE INVENTION

[0002] The invention relates to communication networks in general andmore specifically to networks suitable for use in residential buildings.

BACKGROUND OF THE INVENTION

[0003] As the number of electronic devices in the home has increasedthere has been a demand for a way to permit those devices to communicatebetween themselves and with external networks. Several standards areevolving protocols that will permit devices to communicate over twistedpair and other wiring modalities.

[0004] However, a large number of homes are presently equipped withcoaxial cable to permit the viewing of cable television programming orto permit connection of computer devices to the internet. The evolvingstandards do not appear to take into account this installed base ofcoaxial cable. Instead, such standards require the rewiring of homes, inorder to comply with the evolving protocol, or the use of other existingmedia, such as power lines, telephone lines, or wireless links. Incomparison to coaxial cables, however, such existing media supports asignificantly lower bit rate.

[0005] This invention meets this demand for interconnectivity withoutthe necessity of changing the physical wiring present in the home.

SUMMARY OF THE INVENTION

[0006] The invention relates to a home network. In one aspect, theinvention features a home network including a network backbone, aplurality of modules connected to the network backbone, and ademarcation point unit. Each module is connected between the networkbackbone and a local bus. The demarcation point unit receives a homenetwork signal from one of the modules over the network backbone andreturns the home network signal to the plurality of modules. The networkbackbone includes a plurality of coaxial cables and, in one embodiment,a splitter.

[0007] A module is in communication with a plurality of local buses.Embodiments of the local bus include a 1394 local bus, a universalserial bus (USB), Ethernet bus, Internet protocol (IP) bus. In oneembodiment, at least two of the modules are in communication with 1394local bus.

[0008] The demarcation point unit is in communication with an externalnetwork and receives a cable TV (CaTV) signal from the external network.The CaTV and the home network signals pass together over the networkbackbone to the modules. In one embodiment, the frequency of the homenetwork signal is approximately in the 960-1046 MHz frequency range. Adevice in communication with the demarcation point unit can receive theCaTV signal directly without passing through a module.

[0009] The demarcation point unit includes a signal reflector unit. Inone embodiment, the signal reflector unit that receives the home networksignal from one module—the home network signal is at a first frequency.The signal reflector unit returns the home network signal to theplurality of modules of the home network signal having a secondfrequency. The first frequency can be the same as or different (e.g.,higher or lower) than the second frequency.

[0010] In another aspect, the invention features a home networkincluding a demarcation point unit and a plurality of modules. Thedemarcation point unit receives a signal from a network that is externalto the home. Each of plurality of modules is connected to thedemarcation point unit by one or more coax cables and to a device by alocal bus. One of the modules receives a message from the deviceconnected to that one module by the corresponding local bus andtransmits the message to the demarcation point unit. The demarcationpoint unit receives the message from that one module and transmits themessage and the signal together to each of the plurality of modules overthe coax cables.

[0011] In yet another aspect, the invention features a demarcation pointunit that connects a home network and an external network. Thedemarcation point unit includes a diplexer that receives a first signalfrom the home network and a second signal from the external network. Thediplexer separates the first signal from the second signal. A signalreflector unit receives the separated first signal from the diplexer andreturns the first signal to the diplexer for transmission to the homenetwork.

[0012] In one embodiment, the signal reflector unit includes a coaxcable that reflects the first signal received from the diplexer back tothe diplexer. The coax cable of the signal reflector unit can be shortedto ground or unterminated. In another embodiment, the signal reflectorunit includes a delay line in communication with the diplexer. The otherend of the delay is shorted to ground or unterminated.

[0013] The signal converter unit in another embodiment includes a RFconverter that changes a frequency of the first signal before the firstsignal returns to the diplexer. The signal passing to the diplexer fromthe home network is an upstream signal. The signal returning to thediplexer from the signal reflector unit is a downstream signal. Thesignal reflector unit includes a second diplexer having an input/output(I/O) in communication with a first diplexer and an input incommunication with the RF converter. The second diplexer separates theupstream signal received by the I/O from the downstream signal receivedby the input. The second diplexer returns the downstream signal to thefirst diplexer over the I/O.

[0014] An output in communication with the RF converter passes theupstream signal to the RF converter over the output. The RF converterincludes a RF down-converter in communication with a RF up-converter.The RF down-converter changes the frequency of the upstream signal to anintermediate frequency. The RF up-converter changes the intermediatefrequency to the frequency of the downstream signal. In one embodiment,the frequency of the upstream signal is higher than the frequency of thefirst signal. Also, the power level of the upstream signal received atthe signal reflector unit is constant, and the power level of thedownstream signal leaving the signal reflector unit is also constant.

[0015] In the signal reflector, a splitter can be connected between thediplexer and the home network. The splitter receives the downstreamsignal from the diplexer and transmits the returned downstream signal tothe home network over a plurality of coax cables. The splitter receivesthe upstream signal from the home network for transmission to thediplexer. The diplexer combines the first signal received from thesignal reflector unit with the signal received from the external networkand transmits the combined signal to the home network.

[0016] In another aspect, the invention features a network module thatconnects a network backbone to a local bus. The network module includesa diplexer that receives an analog signal and separates a home networksignal from the analog signal. A modem converts the home network signalto a digital signal. A media access controller (MAC) interfaces with aprotocol of the local bus to deliver the digital signal to the localbus.

[0017] In another aspect, the invention features a method for use bymodules in a home network for communicating with each other over a coaxbackbone. A cycle start burst is transmitted over the backbone to starta transmission cycle during which the network modules transmit burstsover the backbone. A first portion of the transmission cycle isallocated for the transmission of isochronous bursts by the networkmodules. A second portion of the transmission cycle is allocated for thetransmission of asynchronous bursts by the network modules.

[0018] A transmission order is established for the network modules tofollow when transmitting isochronous and asynchronous bursts over thebackbone. The cycle start burst includes the transmission order.Isochronous bursts start at the start of every transmission cycle,followed by the transmission of asynchronous bursts. Transmission of anasynchronous burst is allowed to complete after the end of thetransmission cycle.

[0019] In one embodiment, those network modules that are requestingbandwidth for transmitting isochronous bursts are determined. One of themodules is designated to be a master network module, which transmits thecycle start burst. The network modules synchronize to the cycle startburst.

[0020] In another embodiment, bandwidth is allocated in the firstportion of the transmission cycle to each network module requesting aguaranteed quality of service. Asynchronous bursts are monitored, by agiven network module, on the backbone to determine when a given networkmodule can transmit an asynchronous burst. The given network modulereceives a grant over the backbone to indicate that the given networkmodule can transmit an asynchronous burst.

[0021] In another embodiment, isochronous bursts are monitored by agiven network module on the backbone to determine when that networkmodule can transmit an isochronous burst. An empty burst is transmittedby a given network module if the given network module has no data totransmit during the second portion of the transmission cycle.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The invention is pointed out with particularity in the claims.The drawings are not necessarily to scale, emphasis instead generallybeing placed upon illustrating the principles of the invention. Likereference characters in the respective drawing figures indicatecorresponding parts. The advantages of the invention described above, aswell as further advantages of the invention, may be better understood byreference to the description taken in conjunction with the accompanyingdrawings, in which:

[0023]FIG. 1 is a block diagram of an embodiment of a home networksystem constructed in accordance with the invention;

[0024]FIG. 2 is a block diagram of an embodiment of a demarcation pointunit including a home network reflector unit as shown in FIG. 1;

[0025]FIG. 2A is a block diagram of another embodiment of the homenetwork reflector unit;

[0026]FIG. 3 is a block diagram of an embodiment of a home networkmodule;

[0027]FIG. 4 is a block diagram of an embodiment of a physical layer ofthe home network module of FIG. 3;

[0028]FIG. 5 is a block diagram of embodiments of a modem in the homenetwork module of FIG. 3;

[0029]FIG. 6 is a diagram of an embodiment of a burst or message;

[0030]FIG. 7 is a timing diagram showing an exemplary sequence ofcommunication cycles on a backbone of the home network;

[0031] FIGS. 8A-8B are flow diagrams illustrating an embodiment of aprocess by which the master home network module controls communicationon the coax backbone;

[0032]FIG. 9 is a flow diagram illustrating an embodiment of a processby which each home network module in the home network, other than themaster home network module, communicates over the backbone of the homenetwork;

[0033]FIG. 10 is a flow diagram illustrating an embodiment of a processby which a new home network module registers to become part of homenetwork;

[0034]FIG. 11 is a logical diagram of the home network, in which thebackbone connects four IEEE 1394 local buses through different homenetwork modules;

[0035]FIG. 12 is a conceptual diagram of an emulated bus structure fromthe perspective of each home network module;

[0036]FIG. 13 is a flow diagram illustrating a process performed by eachof the home network modules to initialize a 1394 bus in the homenetwork;

[0037]FIG. 14 is a flow diagram illustrating an embodiment of a processby which each home network module handles 1394 asynchronous packetsreceived from the backbone in an emulated bus embodiment;

[0038]FIG. 15 is a flow diagram illustrating an embodiment of a processby which each home network module handles 1394 asynchronous packetsreceived from a 1394 local bus in an emulated bus embodiment; and

[0039]FIG. 16 is a block diagram of another embodiment of thedemarcation point unit.

DETAILED DESCRIPTION

[0040] In brief overview, FIG. 1 shows an embodiment of a home network10, constructed in accordance with the invention, including ademarcation point unit (DPU) 14 located at the entry point into a home,which operates as the interface between the home network 10 and anexternal network 18, such as a cable television (TV) network or theInternet. The DPU 14 is in communication with a plurality ofhome-network modules (HNM) 28, 28′, 28″, 28′″ (generally 28), eachlocated in one of various rooms of the home. Each HNM 28 is theinterface between devices in a room (e.g., home entertainment devicesand computer devices) and the DPU 14.

[0041] Implementing the home network 10 in the home does not require therewiring of the cable TV equipment that is typically already installedin many homes for accessing the cable TV network 18 or the Internet. TheHNMs 28 communicate with the DPU 14 and with each other over standardcable equipment. Such cable equipment includes coaxial (or coax) cables22, splitters (generally 24), and cable TV outlets 26. This installedcable equipment operates as a backbone of the home network 10 forconveying intra-room communications. Although the home network 10 canoperate with existing coax wiring, the principles of the invention applyalso to other types of wiring, such as CAT-5 or plastic fiber. Ingeneral, the home network 10 operates in parallel to the cable TVservices, leaving legacy cable TV signals and devices (such as set topboxes and cable modems) unaffected.

[0042] With this existing coax cable equipment, the home network 10joins various computer devices, such as personal computers andperipherals (printer, scanner, CD etc.), and entertainment equipment,such as set top boxes (STB), televisions, video cassette recorders,personal video recorder (PVR), etc., located throughout the home intoone network. By this one network, various computer devices in differentrooms can share access to the Internet, and video or audio sourcesplayed in one room can be enjoyed in another room of the home. In oneembodiment, described in more detail below, the existing cable equipmentprovides an intra-room backbone for an IEEE-1394 (FireWire) network.

[0043] More specifically, in an exemplary embodiment of the home network10, HNMs 28, 28′, 28″, 28′″ in respective rooms 30, 30′, 30″, 30′″(generally 30) are connected to the home network backbone through cableTV outlets 26. The home network backbone (referred to hereafter asbackbone 20), includes a plurality of coax cables 22 that connect thecable TV outlets 26, and thus the HNMs 28, to the DPU 14. The coaxcables 22 connect to the splitters 24, which distribute the signalsreceived from the external network 18 and from the HNMs 28 to each ofthe rooms 30 connected to the home network 10. In the embodiment shownin FIG. 1, the DPU 14 includes one of the splitters 24′; in anotherembodiment, instead of being part of the DPU 14, that splitter 24′ isconnected to an output of the DPU 14. In some embodiments, a residentialgateway device is located at the demarcation point (i.e., the entrypoint of the coax cable to the home) to exchange signals between theexternal network 18 and other devices in the house, such as a cablemodem or a STB. Embodiments of the residential gateway provide Internetaccess (e.g., cable modem, digital subscriber line (DSL)). Otherembodiments provide the functionality of a set top box, of a personalvideo recorder, or of a tuner for multiprogramming. In each of theseembodiments, the DPU 14 can be integrated into or be external to suchthe residential gateway device.

[0044] Each room 30 includes one or more devices 33. Devices 33 include,for example, digital video disc (DVD) players, video cassette recorders(VCR), game consoles, interactive televisions computers, scanners, faxmachines, printers, analog televisions, digital televisions, set topboxes, stereo systems, and camcorders. In each room 30 having a device33 that the resident of the home wants to make available for intra-roomcommunication, there is located a HNM 28 that connects that device 33 tothe backbone 20. For example, rooms 30, 30′, 30″, and 30′″ each havedevices 33 that the resident chooses to have intra-room communicationcapability; so, in each of these rooms an HNM 28 connects those devices33 to the backbone 20.

[0045] Devices 33 within a given room 30 that communicate according tothe same protocol (e.g., USB (universal serial bus), IP (InternetProtocol), Ethernet, and IEEE-1394) are typically connected to the samelocal bus 35. Each HNM 28 can interface with one or more different typesof local buses (generally 35). For example, in room 30 the HNM 28interfaces with a local 1394-bus 35′, connected to an analog set-top boxand a DVD player, and a local data-bus 35″ (e.g., Ethernet, USB, IP),connected to analog set-top box and a personal computer. In oneembodiment, devices 33 in different rooms of the same local bus type(e.g., 1394) can communicate with each other over the backbone 20,whereas devices 33 of different local bus types (e.g., 1394 and USB) donot. In some embodiments, the HNM 28 resides in the entertainment ordata device, in other embodiments, the HNM 28 resides in a separate box.

[0046] In addition to the various types of local buses 35, the HNM 28can connect to other devices 33 in the room 30 by coax cable. Forexample, the HNM 28 in room 30 also connects to the analog set-top boxby coax cable 36. Although shown in FIG. 1 to be separate from theanalog set-top box, in one embodiment the HNM 28 is a built-in componentof the set-top box.

[0047] Each HNM 28 communicates with the DPU 14 and each other HNM 28 onthe backbone 20 with analog signals and converts analog signals receivedfrom the DPU 14 and the HNMs 28 into digital signals for delivery todevices 33 connected to that HNM 28. If a room 30 has a legacy device 33requiring an analog signal (such as an analog or digital TV), but doesnot have a set-top box, an interface box can convert the digital signalproduced by the HNM 28 into a signal that is appropriate for that legacydevice. For example, in room 30′, the HNM 28′ communicates with theanalog TV, which requires an analog signal, through the interface box32, which converts 1394 digital signals to audio/visual analog signals.

[0048] Instead of being on the same local bus 35, devices 33 of the sameprotocol within a given room 30 can connect to the same HNM 28 bydifferent local buses 35. With this arrangement, such devices 33 cancommunicate with devices 33 in other rooms 30 of the home.

[0049] Devices 33 that the resident does not want to participate inintra-room communication can connect directly to the external network 18without the use of the HNM 28. For example, in room 30 ^(iv) , theanalog television set is connected directly to the backbone 20 withoutan intervening HNM 28. Such devices 33 continue to receive the legacycable TV signals from the cable TV network or have broadband access tothe Internet through the DPU 14.

[0050] In operation, each HNM 28 permits those devices 33 connected tothat HNM 28 to communicate with other devices 33 in different rooms 30,to receive programming from the cable television, and to have broadbandaccess to the Internet (e.g., through a cable modem, DSL service, andSatellite). For example, a DVD disc playing in the DVD player in room 30can be viewed on the digital television in room 30″ and that digitaltelevision can also receive programming from the cable televisionnetwork 18. Similarly, computer devices in various rooms can communicatewith one another using their respective HNMs 28 connected to thebackbone 20. For example, the personal computer (PC) in room 30 canprint a document on the printer or share a file with the personalcomputer in room 30′″, or access the Internet through a cable modem (orDSL or audio modem). In accordance with the principles of the invention,the analog signal to and from the Internet (or cable provider) runs overthe same coax wires 22 in the house and at the same time as theintra-room communication signals (hereafter the home network signal). Ineach case, the signal received from the cable television network orInternet provider are routed to the proper electronic devices by way ofthe DPU 14 and the appropriate HNM 28.

[0051]FIG. 2 shows an embodiment of the DPU 14 including a diplexer 40,a home-network reflector unit (HRU) 44 and a splitter 24″. In general,the diplexer 40 separates a cable TV (CaTV) signal (or satellite signal)received from the external network 18 from a home network signalreceived from the HNMs 28 connected to the backbone 20. One input/output(I/O) port (the “L” port) of the diplexer 40 transmits and receives theCaTV signal (or satellite signal) to and from the external network 18.Another I/O port (the “H” port) of the diplexer 40 transmits andreceives the home network signal to and from HRU 44. The diplexer 40also combines the CaTV (or satellite) signal received from the externalnetwork 18 with the home network signal received from the HRU 44 andpasses the combined signal to the splitter 24′ through a third I/O portfor subsequent transmission to the HNMs 28 over the backbone 20.

[0052] The “L” port uses a low-pass filter at a certain predeterminedfrequency, fc, and the “H” port uses a high-pass filter at the samefrequency, fc. By setting the frequency, fc, to about 900 MHz, forexample, the low-pass “L” port transfers TV signals (5-860 Mhz), and thehigh-pass “H” port transfers the home network signal above 860 MHz. Morespecifically, one embodiment sets the cutoff frequency to 950 MHz toseparate frequencies above 950 MHz for use by the home network signalfrom the CaTV signals, which are in the 5-860 MHz range.

[0053] If satellite TV signals are used inside the home, the frequency,fc, is set to about 2100 MHz, to separate the satellite TV signals(950-2100 MHz) from the home network signal (below 950 MHz or above 2100MHz). In this satellite example, the “L” port is connected to theexternal network 18 and the “H” port is connected to the HRU 44.Alternatively, the cutoff frequency, fc, is set to about or below 900MHz, and the home network signal uses frequencies below the satellite TVsignals. In this satellite example, the “H” port is connected to theexternal network 18 and the “L” port is connected to the HRU 44.

[0054] In some embodiments, the HRU 44 is either an unterminated or ashorted coaxial cable, which reflects the home network signal receivedfrom the diplexer 40 back to the diplexer 40. Some embodiments of apassive HRU connect one port of a passive delay line to the H port ofthe diplexer 40 to improve the performance of the network 10 by avoidingsignal fading. In such embodiments, the other port of the passive delayline is unterminated or shorted. In still other embodiments, leaving anoutput of the diplexer 40 unterminated or by shorting that output toground attains reflection of the home network signal. These embodimentsof the HRU 44 are referred to as passive HRUs.

[0055]FIG. 2A shows another embodiment of the HRU 44 including adiplexer 42, band pass (BP) filters 46, 48, amplifiers 50, 52, an RFdown-converter 54, an RF up-converter 56 and an intermediate frequencyfilter and amplifier unit 58. The diplexer 42 along with the BP filters46, 48 separate the upstream signal from the downstream signal. Theupstream signal is the signal coming from the backbone 20 to the HRU 44,and downstream signal is the signal returning from the HRU 44 to thebackbone 20. The upstream signal coming from a transmitting HNM 28enters the diplexer 40 and passes to the internal diplexer 42 of the HRU44. The signal from the diplexer 42 is band pass filtered by BP filter46, amplified by amplifier 50, and RF down-converted by down-converter54 to an intermediate frequency (IF). In one embodiment, theintermediate frequency is 630 MHz. Other different frequencies can beused without departing from the principles of the invention. Usage ofthe intermediate frequency simplifies the RF design, by keeping thesignal, its images, and the local oscillator frequency separate fromeach other. Having the BPFs 46, 48 external to the diplexer 42simplifies the implementation of the diplexer 42.

[0056] The IF filter and amplifier unit 58 then amplifies and band passfilters the IF signal. The RF up-converter 56 shifts the frequency ofthe IF signal up to the downstream frequency band. The amplifier 52 andBP filter 48 then amplify and filter the downstream signal. Theamplifiers 50, 52 with the amplification provided by the IF filter andamplifier unit 58, sufficiently amplify the home network signal toimprove the reach of the home network signal inside the home. Thisdownstream signal then passes through the diplexers 42, 40 back to thebackbone 20 of the home network 10. Thus, the HNMs 28 communicate witheach other by issuing messages to the backbone 20 (i.e., the upstreamsignal). The HRU 44 receives the upstream signal, amplifies and shiftsthe RF frequency of the upstream signal, and then returns the upstreamsignal with the shifted frequency to the backbone 20 as the downstreamsignal. The HNMs 28 then receive the messages in the downstream signalfrom the backbone 20. Before the downstream signal reaches the backbone20, the diplexer 40 combines the downstream signal with the CaTV signal(or satellite) for transmission over the in home coax wires 22.

[0057] The home network 10 employs transmission power control. Each HNM28 adjusts its transmission power to such a power level that when itstransmitted signal arrives at the HRU 44, that signal has a predefinedpower level. Thus, the input power of the upstream signal arriving atthe HRU 44 remains constant because each HNM 28 uses an appropriatetransmission power level to account for the attenuation of the signalover the backbone 20 and thereby achieves the predefined power level atthe HRU 44. Also because power level of the inputted upstream signal isconstant and the amplification performed by the HRU 44 is constant, thedownstream signal leaving the HRU 44 is also constant.

[0058] In one embodiment, the upstream signal at the input to the HRU 44is −50 dBm, and the downstream signal at its output is −10 dBm.Accordingly, a HNM 28 can transmit at a power between −10 dBm, iflocated far from the HRU 44, and −50 dBm if located close to the HRU 44.The actual transmitted power is determined according to the attenuationbetween the remote HNM 28 and the HRU 44. For instance, if theattenuation is 10 dB, the HNM 28 should transmit −40 dBm. If the HNM 28is located 40 dB from the HRU 44, that HNM 28 should transmit at a powerof −10 dBm so that the upstream signal can reach the HRU 44 with a powerof −50 dBm.

[0059] The HRU 44 transmits at a constant power (e.g., −10 dBm).Therefore, if the HNM 28 is located 25 dB from the HRU 44, that HNM 28receives the downstream signal at a power of −35 dBm (−10 dBm −25dBm=−35 dBm), irrespective of which HNM 28 sent the upstream signal tothe HRU 44 that reflected back as the downstream signal.

[0060] Employing this transmission power control simplifiessignificantly the gain control function at the receiver and at thetransmitter of the home network signal, particularly if each HNM 28 canset the gain just once during initialization.

[0061] In one embodiment, the home network signal transmitted over thehome network backbone 20 is in the 960 to 1046 MHz frequency range, butother frequency bands above the CaTV signals can be used. The CaTVsignal (including the signal from Internet providers) is in thefrequency range of 5 to 860 MHz. Table 1 shows that frequencies above960 MHz are available for use in those homes in which CaTV signals areinstalled. It should be noted that at frequencies greater than 1000 MHz,low quality splitters found in the home provide poor signal isolationand return loss performance. TABLE 1 Frequency Range (MHz) Signal870-896 Cellular mobile phone uplink 896-902 Private land mobile radio902-928 Amateur radio service reserve 928-932 Domestic public radioservice (paging) 944-947 Broadcast radio service (intercity relay) 950-2100 DBS (Satellite over coax)

[0062] In another embodiment, the home network signal is in the 5-45 MHzfrequency range. This frequency band is used by the U.S. cabletelevision operators for reverse path signals, i.e., signals that thehome devices 33, such as set top boxes (STB) and cable modems (CM),transmit back to the cable provider (i.e., the head-end). For theEuropean standard (called DVB), the reverse path frequency is located inthe band from 5-65 MHz.

[0063] Reverse channel signals transmitted to the head-end include theReverse Data Channel Out Of Band (RDC OOB) signals from the STB and theReverse Data Channel of the CM (RDC CM). To ensure proper operation ofthe set-top boxes and cable modems over the home network 10, the reversechannel signals should return seamlessly to the head-end. The head-enddetermines the actual frequencies used for the reverse channel signalsand the bandwidth for each channel is small compared to the 5-45 MHzfrequency range. Typically, but not necessarily, the set-top boxes andcable modems in the home use the same programmable frequencies for thereturn channel. The head-end determines the frequency allocation andtransmits information regarding the allocated frequencies to the devices33 in the home.

[0064] To transmit this information, the head-end uses frequencies above50 MHz. This communications channel, at frequencies above 50 MHz, istermed the Out of Band Forward Data Channel (OOB FDC). Becausefrequencies above 50 MHz pass freely through the home network 10, thisOOB FDC signal carrying RDC OOB and RDC CM information passes unimpededto the set top boxes and the cable modems connected directly (that isnot through a HNM 28) to the coaxial cable 22.

[0065]FIG. 3 shows an exemplary conceptual embodiment of animplementation of the HNM 28, which functions as bridge between the coaxbackbone 20 and each local bus 35. In brief overview, the HNM 28receives a signal from a device 33 through a data port and converts thatsignal into a modulated analog signal over the backbone 20, combinedwith the Cable TV signal. In the other direction, the HNM 28 receives ananalog signal over the backbone 20 and converts the analog signal into adata signal. In one embodiment, the HNM 28 is implemented as an IC(integrated circuit) chip set that is incorporated in an entertainmentor data device, or in a standalone box.

[0066] The backbone-side of the HNM 28 includes a physical layer 90, amedia access control (MAC) layer 92, and a network layer 94. The MAClayer 92 supports constant bit rate (CBR) transmission and anunspecified bit rate (UBR) transmission with CBR 96 and UBR 98protocols, respectively. To support quality of service (QoS)requirements, the CBR protocol 96 is used for the transmission ofisochronous data and the UBR protocol 98 for the transmission ofasynchronous data. The network layer 94 includes a switching fabric 100for controlling the flow of isochronous and asynchronous traffic betweenthe backbone 20 and each local bus 35.

[0067] The architecture of the protocol stack on the local-bus-side ofthe HNM 28 depends on the type of local bus. For example, if the localbus is an IEEE 1394 bus, then the HNM 28 includes a 1394 Phy layer 102,a 1394.1 link layer 104 (with bridge functionality), and a network layer106 that supports isochronous 107 and asynchronous 108 transmissions. Inone embodiment, the local bus is an Ethernet bus, which hasEthernet-specific Phy and MAC layers. In another embodiment, the localbus is a universal serial bus (USB), which correspondingly hasUSB-specific Phy and data link layers. In an embodiment in which the HNM28 is integrated in a device, such as a set top box and a personalcomputer, the bus is specific and internal to that device, and thebus-side of the protocol stack includes a device-specific interface forcommunicating on the bus.

[0068] In other embodiments, the HNM 28 operates as a bridge between thebackbone 20 and a plurality of local buses of different types. Forexample, as shown in FIG. 3, the HNM 28 is a bridge for 1394, 802.3, anda USB local buses. The HNM 28 can support other types of local buses anddifferent combinations of local bus types without departing from theprinciples of the invention. If the HNM 28 resides in a device, such asin a STB, the various local buses are connected directly to a local businternal to that device.

[0069]FIG. 4 shows an exemplary embodiment of the physical layer 90 ofthe HNM 28, including the diplexer 110, RF/Analog unit 112 (hereafter RFunit) and a modem 114. The diplexer 110 is connected to the coax outlet26 in the room 30 and separates the CaTV signal (frequencies 5-860 MHz)from the home network signal. The CaTV signal includes the broadcastvideo, video in demand, cable modem and all other signals that aredelivered by the Cable TV operator to the home, and return path signals,like the cable modem return channel, Interactive TV etc. The CaTV signalcan pass to other electronic devices in the room 30, such as a TV cablemodem and an analog set-top box (STB). The home network signal passes tothe RF unit 112.

[0070] The RF unit 112 includes a diplexer 116, which is connected to adownstream path 118 (here, from the backbone 20 to the local bus 35) andan upstream path 120 (from the local bus 35 to the backbone 20). Fromthe home network signal, the diplexer 116 and filters 122, 142 separatethe downstream signal from the upstream signal. The downstream signalpasses towards the local bus 35 and the upstream signal towards thebackbone 20.

[0071] The bandpass filter (13PF) 122 filters the downstream signal(lower frequencies) to remove the upstream signal and out-of-band noise.The downstream signal passes through a low noise amplifier 124 and RFdown-conversion circuitry 126. The RF down-conversion circuitry 126converts the downstream signal to baseband frequencies. Embodiments ofthe RF down-conversion circuitry 126 include an I/Q demodulator or amixer.

[0072] If the RF down-conversion circuitry 126 is operating as an I/Qmodulator, the I-channel and Q-channel pass separately to the broadbandfilter/amplifier unit 128, which low-pass filters the I-channel andQ-channel separately to remove the image of the signal. The I-channeland Q-channel then pass through a dual analog-to-digital (A/D) converter129. The dual A/D 129 has a separate A/D converter for the I-channel andfor the Q-channel. The digital output of the A/D converter 129 entersthe modem 114. The modem 114 includes a digital signal processing (DSP)portion 130 and a framer 132.

[0073] In general, the modem 114 uses an efficient modulation scheme,like QAM, multi QAM, Orthogonal Frequency Division Multiplexing (OFDM)or Discrete Multitone (DMT). In one embodiment, the backbone 20 supports100 Mbps bit rate. If, for example, the modem 114 uses QAM 256 (8 bitsper symbol), only 12.5 MHz (100/8) of bandwidth is required. The use ofefficient bandwidth modulations achieves higher data rates for aspecific frequency band produces less cross talk between potentiallyinterfering signals. Another advantage is that the modem 114 enables thehome network 10 to coexist with pre-existing low-quality splitters oftenfound in the cable networks of the home. Such splitters are frequencylimited—at frequencies above 1000 MHz the performance of such splittersdegrades significantly. Reflections can occur at the splitter, resultingin inter-symbol interference to the home network signal.

[0074] The upstream path 120 passes from the modem 114 to the diplexer116 through a dual D/A converter 134, a baseband filter/amplifier unit136, RF up-conversion circuitry 138, an amplifier 140, and a band-passfilter 142. On the upstream path 120, the DSP 130 generates one or twooutput words corresponding to one or two D/A converters 134, dependingupon the embodiment of the RF up-conversion circuitry 138. Embodimentsof the RF up-conversion circuitry 138 include an I/Q modulator or amixer. If I/Q modulation is used in the RF up-conversion circuitry 138,then two output channels are implemented, with two D/A converters 134.If the mixer is used, then only one D/A converter 134 is needed.

[0075] The analog baseband signal generated by the D/A converters 134passes through baseband filters 136 and then is up-converted by the RFup conversion circuitry 138 to the upstream frequency band. The poweramplifier 140 amplifies the RF up-converted signal and the bandpassfilter 142 filters the signal and the diplexer 116 combines the upstreamsignal with the CaTV signal for transmission over the home coax backbone20. The gain of the amplifiers 124 and 140 are programmable, and themodem DSP 130 sets this gain.

[0076]FIG. 5 shows two embodiments of the modem 114, including the DSP130 and the framer 132. Signals take two paths through the modem 114;the downstream path 118 from the dual A/D converter 129 to the MAC 92through the framer 132 and the upstream path 120 from the framer 132 tothe dual D/A converter 134.

[0077] In FIG. 5, two embodiments of the modem 114 are shown. In a firstembodiment, I/Q modulation occurs at the RF unit 112. This embodimentincludes an I/Q compensation block 144 (shown in phantom) thatcompensates digitally for different I/Q modulation imperfections, suchas local oscillator leakage, I/Q phase and amplitude imbalance, and DCsignal components. The I/Q compensated signal passes to receiverfront-end circuitry 146, which includes a match filter and aninterpolator (both not shown). The match filter filters noise and otherundesired out-of-band signals. The interpolator outputs a signal that issampled at an integer multiple of the received sample rate based ontiming recovery information received from a timing VCO block 148 and atiming PLL block 150 provide. The timing recovery is useful because theA/D converter 129 samples the downstream signal at its particularsampling frequency, which approximates but may not equal the symbol rateof the HNM 28 that transmitted the signal.

[0078] In a second embodiment of the modem 114, I/Q modulation occurs atthe DSP 130 of the modem 114 (because the RF unit 112 uses a standardmixer; thus, this embodiment has no I/Q compensation block 144. Also,the receiver front-end 146 of this embodiment includes a down-converterblock and low-pass filter (both not shown) to perform the I/Qdemodulation.

[0079] The output of the receiver front-end 146 passes to a burst AGCblock 152, which provides digital gain control per burst to optimize thesignal level at the input to the equalizer 154. From the burst AGC block152, the signal passes to a decision feedback equalizer (DFE) 154. TheDFE 154 includes a feed forward equalizer (FFE) 156 and a decisionfeedback filter (DFF) 158. To overcome frequency offset between thetransmitting and receiving HNMs 28, the DFE 154 includes a rotator 160,which is applied at the output of the FFE 156. A carrier recovery PLL162 sets the correction frequency of the rotator 160. The output of therotator 160 minus the output of the DFF 158 enters a slicer circuit 164to make a decision on the received symbol. The error signal 166 is equalto a distance between the decided symbol and the input to the slicercircuitry 164. The error signal 166 gives an indication to the amount ofnoise and the quality of the received signal and decisions. The errorsignal 166 is also used for the adaptation of the equalizers duringpacket receiving. The received symbols sent to the framer 132 forde-mapping, de-forward error correcting (FEC), and de-framing, toextract the transmitted data bits, which are delivered to the MAC(Medium Access Controller) 92 for upper layer processing.

[0080] On the upstream path 120, the framer 132 receives data bits fromthe MAC 92, which frames the bits. A mapper 170 maps the encoder-framedbits to generate the transmitted QAM symbols. A transmitter front-end172 processes the QAM symbols. The transmitter front-end 172 includes apulse shaper 174, a digital power gain adjuster 176 for fine tuning thetransmitted power, and a clipper 176 to reduce the peak-to-average ratioof the transmitted signal to relax RF transmitter requirements. Aninterpolator 180 synchronizes the transmitted symbol rate with thesymbol rate of the master HNM 28. The modulator timing VCO loop 182performs the synchronization.

[0081] Because QAM symbols are complex numbers, the signal leaving theinterpolator 180 is a complex signal, that is, the signal is made of twostreams of data (a real channel and an imaginary channel). If the DSP130 is implementing I/Q demodulation, the DSP 130 includes an I/Qfrequency up-converter 184 to create a real signal. An inverted-sincfilter 186 then shapes the resulting I/Q signal band and delivers theshaped signal to the D/A converter 134.

[0082] If the DSP 130 is not implementing I/Q demodulation, because theRF unit 112 is performing the I/Q demodulation, the I/Q frequencyup-converter 184 is not used. The signal from the interpolator 180remains complex and the dual D/A converter convert the two (real andimaginary) signal streams into two analog channels (I and Q). Also, inthis embodiment, a transmitter I/Q compensator 188 is employed to handleRF imperfections.

[0083] The DSP portion 130 of the modem 114 also includes a preambledetector and channel estimation block 190 (hereafter preamble detector),which is communication with the I/Q compensation block 144 (if any), thereceiver front-end 146, a cycle start detector 192, and the burst AGCblock 152. The preamble detector 190 also controls the gain of theamplifiers 124 and 140 of the RF unit 112 to provide power control, asdescribed above. The preamble detector 190 provides channel estimations,RF imperfection estimations, and synchronization information for the PLLloop 150. The preamble detector 190 initializes the DFE 154 for eachburst. Other functions of the preamble detector 190 include detecting anexisting burst in the downstream path 118, distinguishing between typesof bursts (described below), and detecting a cycle start signal.Depending upon the type of burst detected, the modem 114 adopts adifferent behavior.

[0084] The MAC (FIG. 3) layer 92 controls the transmission protocol(hereafter MAC protocol) by which the HNMs 28 communicate with eachother over the coax backbone 20. In the home network, one of the HNMs 28connected to the coax backbone 20 is designated as a master HNM 28. Inone embodiment, such designation can occur by manually configuring thatone HNM 28 to operate as the master HNM 28. In another embodiment, theHNMs 28 elect the master HNM 28. Functionality of the master HNM 28includes: 1) assigning addresses to each of the HNMs 28 and devices inthe home network; 2) synchronizing the HNMs 28; 3) managing isochronousand asynchronous transmissions over the backbone 20 to avoid collisionsbetween transmitting HNMs 28; 4) allocating bandwidth to the HNMs 28;and 5) registering new HNMs 28. Also, a master HNM that is incorporatedin or in communication with a STB (or other device that has access tothe cable head-end) operates as a window into the home network throughwhich someone at the cable head-end can monitor and diagnose theoperation of the home network 10.

[0085] Communication on the coax backbone 20 between HNMs 28 isisochronous or asynchronous, in accordance with the MAC protocol. Toexchange messages with each other, the HNMs 28 transmit isochronous andasynchronous bursts over the backbone 20. Each burst has a predefinedstructure (described below) that encapsulates one or more packets. Theheader of the packets includes the destination address of the targetdevice for that packet—each packet has its own destination). The data insuch packets convey the messages (i.e., the meaning of thecommunications). The devices 33 on the local buses 35 produce and sendthe packets to the appropriate HNM 28 to be prepared into bursts. Asingle burst can include packets that originate from more than onedevice 33 on a local bus 35 or that are targeted to more than one device33 on a local bus 35. In general, the MAC protocol ensures that burststransmitted by different HNMs 28 over the backbone 20 do not collide, orif collisions do occur because of errors or noise over the backbone 20,the home network can recover and resume normal operation.

[0086] The MAC protocol supports at least seven types of bursts: 1)cycle start bursts; 2) data bursts; 3) registration start bursts; 4)registration bursts; 5) fairness cycle start bursts, 6) empty bursts,and 7) self-train bursts, each described in more detail below. Only themaster HNM 28 issues cycle start, fairness cycle start, and registrationstart bursts.

[0087] The cycle start burst indicates the start of an isochronous cycleand of a transmission cycle (described below). Each cycle start burstcarries CBR data of the master HNM 28. The CBR data in the cycle startburst can include management data, an identity of each HNM 28 that isgoing to transmit a data burst during the upcoming CBR period 228, and atransmission order for the HNMs 28 to follow during the CBR period 228.The other HNMs 28 in the home network 10 synchronize to this cycle startburst.

[0088] Fairness cycle start bursts mark the start of a fairness cycle(and a UBR period). Registration start bursts indicate a beginning of aregistration period that is available for a new HNM 28 to use, asdescribed below.

[0089] Any HNM 28, including the master HNM 28, can issue data bursts,empty bursts, and self-train bursts. Data bursts carry data andmanagement information. Empty bursts carry no data. A HNM 28 transmitsan empty burst when it has no data to transmit during its allotted time.The master HNM 28 transmits an empty burst if another HNM 28 does notuse its allotted to time (and does not issue an empty burst). Self-trainbursts operate to calibrate the HNM 28 to the transmissioncharacteristics of the home network.

[0090] HNMs 28 other than the master HNM 28 issue registration bursts toregister with the master HNM 28, and thus with the home network 10.Within the registration burst, the registering HNM 28 can request aguaranteed bandwidth and indicate the amount of bandwidth desired.

[0091]FIG. 6 shows an exemplary embodiment of the structure of eachburst 200 that the HNMs 28 transmit over the coax backbone 20. Eachburst 200 is a sequence of segments that includes a preamble 202 (havinga periodic preamble 210 and an aperiodic preamble 212), a Phy header204, data 206, and a postamble 208.

[0092] The preamble 202 signifies the start of the burst 200 and thetype of burst 200. In general, the preamble 202 enables the modem 114 ofthe HNM 28 to synchronize the carrier and timing loops 162, 150,respectively, and the equalizers 156, 158 to the transmitted burst 200.The preamble 202 also enables the setting of the gains of the analogamplifiers 124, 140 in the RF unit 112.

[0093] The periodic preamble 210 is a predetermined sequence thatenables the modem 114 within the HNM 28 to achieve carrier sense,carrier and timing synchronization, received-power level estimation, andinitial channel estimation. In one embodiment, the length of theperiodic preamble 210 indicates the type of burst. The length isdetermined by the number of times a sequence of symbols (e.g., 32symbols) is repeated. For example, in one embodiment, if the 32-symbolsequence is repeated 4 times then the burst is a data burst, 6 timesmeans that the burst is a cycle start burst, 8 times indicates afairness cycle start burst, and 10 times indicates a registration startburst.

[0094] The pattern of symbols in the periodic preamble 210 can also beused to indicate the type of burst. For example, two different bursttypes can have the same periodic preamble length, but be distinguishedby different symbol patterns (e.g., inverting the sign of the signal forevery other repeated symbol sequence). For example, in the embodimentdescribed above, the periodic preamble of the empty burst has a 32symbol sequence that is repeated four times, which is the same length asthe periodic preamble of the data burst. Also, for the self-train burstthe 32-symbol sequence is repeated 8 times, which is the same length asthe periodic preamble of the cycle start burst. For the empty andself-train bursts, however, the sign alternates for every other repeatedsymbol sequence, which distinguishes these bursts from the data andcycle start bursts (which do not use an alternating sign), respectively.

[0095] There are two classes of bursts: bursts that require channelestimation and bursts that do not. Bursts that require the channelestimation by the receiving HNM 28 include data bursts, cycle startbursts, fairness start bursts, registration bursts, and registrationstart bursts. Each of these burst types has a preamble 202 of a fixedlength; that is, cycle start bursts have a preamble of a first fixedlength, fairness start bursts have a preamble 202 of a second fixedlength, etc. The distinguishing of burst types by the length of thepreamble 202 assures that the receiving HNM 28 achieves real-timeperformance without the need for extended complexity and buffering. Forattaining real-time performance, encoding the burst type by the periodicpreamble length is more advantageous than embedding the burst type inthe header, as is the usual practice with lower rate systems. Encodingthe burst type by the periodic preamble length rather than embedding theburst type in the header avoids a time consuming process of extractingthe data embedded in the header to determine the burst type.

[0096] Bursts that do not require channel estimation include empty (ornull) bursts and self train bursts, which in general have a shorterpreamble 202 than the other types of bursts. As described above, theperiodic preamble 210 of the preamble 202 for these bursts have analternating sign (signals of the odd periods are the inverse of signalof the even periods). Although not useful for channel estimation, thistype of preamble 202 is useful for burst type identifications.

[0097] The modem 114 uses the predetermined aperiodic preamble 212,which is a pseudo-random sequence, to refine the channel estimation andto initialize the modem equalizers 154, 156.

[0098] The Phy header 204 includes the parameters that are required bythe DSP 130 and FEC 132 to decode the bursts (i.e., a scrambler seed,FEC parameters, interleaver parameters, constellation sizes, etc.). Insome embodiments, the Phy header 204 also includes the source address ofeach device 33 originating the burst. In one embodiment, the Phy header204 conveys 36 bits of information on 18 QPSK (Quadrature Phase ShiftKeying) symbols.

[0099] The data 206 carries the QAM symbol data. The constellation isthe same for each HNM 28 (when transmitting), except when the HNM 28 istransmitting a registration burst. (Registration bursts are always QPSK,which is the default constellation size for new HNMs 28 requesting tojoin the home network 10.)

[0100] The postamble 208 is a predefined sequence of BPSK (Binary PhaseShift Keying) symbols that the modem 114 uses (along with any gap thatfollows the burst 200) to recognize as the end of the burst 200.

[0101]FIG. 7 shows an embodiment of an exemplary sequence 220 of bursts,separated by transmission gaps, produced by four HNMs 28 (HNM 0, HNM 1,HNM 2, and HNM 3) on the coax backbone 20 in accordance with the MACprotocol. Transmission of the bursts over the backbone 20 occurs as asequence of cycles. Each cycle carries information that enables the HNMs28 to recover timing and other parameters accurately for the successfulreceiving and transmitting of bursts.

[0102] As shown, the sequence of cycles includes three types ofcommunication cycles, 1) transmission cycles 222, 2) fairness cycles224, and 3) ACK cycles 226, and four types of periods, 1) constant bitrate (CBR) periods 228, 2) unspecified bit rate (UBR) periods 230, 3)registration periods 232, and 4) ACK periods 226.

[0103] Each transmission cycle 222 starts when the master HNM 28transmits a cycle start burst and ends before the master HNM 28transmits the next cycle start burst. Each transmission cycle 222 has apredetermined duration (e.g., approximately 1 ms) and starts with a CBRperiod 228. During this CBR period 228, each HNM 28 that has beenallocated bandwidth by the master HNM 28 transmits one CBR burst. (CBRbursts can include one or more CBR packets aggregated together andtransmitted during the CBR period.) Each HNM 28 that has been allocatedtime within the CBR period 228 transmits one burst, but the size (orlength) of that burst depends upon the amount of bandwidth allocated tothat HNM 28 and upon the amount of data ready for transmission in thatparticular transmission cycle. If at a particular transmission, the HNM28 does not have any data ready for transmission, the HNM 28 transmitsan empty (or null) burst. This empty burst notifies the next HNM 28 inthe transmission order that the next HNM 28 can now transmit during theCBR period 228. The HNMs 28 transmit bursts over the backbone 20 in anorder predefined by the master HNM 28. For example, as shown in FIG., 7,the transmission order during each CBR period 228 is HNM0 (the masterHNM) followed by HNM1 and then by HNM3. (In this example, HNM2 has noallocated bandwidth during the CBR period 228.) The master HNM 28 canchange the amount of allocated bandwidth and the order of transmission,such as when a new HNM 28 registers for guaranteed quality of service.The master HNM 28 communicates such changes to the other HNMs 28 in thedata field 206 of the cycle start burst.

[0104] If, at the end of the CBR period 228, time remains in the currenttransmission cycle, a UBR period 230 or a registration period 232 and/oran ACK period 226, follows the CBR period 228. The UBR period 230 ispart of a fairness cycle 224, as described below. During the UBR period230, each HNM 28 can send a self-calibration (or training) burst beforesending a UBR burst. (A UBR burst is a burst that is transmitted duringthe UBR period 230.)

[0105] A fairness cycle 224 represents the time over which every HNM 28transmits one UBR burst over the coax backbone 20. (If a HNM 28 has nodata to transmit, the HNM 28 transmits a null burst in its allottedtime.) The fairness cycle 224 can span one or more transmission cycles222. Accordingly, during a fairness cycle 224, UBR periods 230 areinterleaved with CBR periods 228.

[0106] More specifically, each fairness cycle 224 begins with a UBRburst from the master HNM 28 (called a fairness start burst) andcompletes after all of the other registered HNM 28 transmits a UBRburst. The HNMs 28 transmit the UBR bursts according to a certain order,starting with the master HNM 28 (here, HNM 0). The UBR bursts do notdisturb the synchronization of the transmission cycle; that is,transmission cycles 222 and, thus, CBR periods 228, occur regularly(with some jitter, described below), even if each registered HNM 28 hasnot yet transmitted an UBR burst. (In such an instance, a fairness cycle224 spans more than one transmission cycle 222.) Jitter occurs when oneof the HNMs 28 is presently transmitting a UBR burst while the start ofa new transmission cycle 222 is due to begin. Instead of starting thenew transmission cycle 222, the HNM 28 is permitted to complete the UBRburst, which extends the present transmission cycle 222 beyond thepredefined transmission cycle period. Jitter is the measure of theamount of time that the UBR period extends beyond the expected end ofthe transmission cycle 222 (i.e., start of the next CBR period 228).

[0107] At the end of a fairness cycle 224, the master HNM 28 transmits aregistration start burst to initiate a registration period 232, whichextends for a predefined period. (The registration start burst marks theend of the fairness cycle 224.) The master HNM 28 determines when tostart the registration period 232. In some embodiments, a registrationperiod 232 can occur as often as after each fairness cycle 224. In otherembodiment, the registration period 232 occurs less frequently, such asafter a plurality of fairness cycles 224. As described above, generally,with respect to UBR periods 230, the registration period 232 can extendbeyond the end of the current transmission cycle 222, thus delaying thestart of the next transmission cycle 222.

[0108] The registration period 232 is available for use by new HNMs 28(i.e., HNMs 28 that have been added to the home network and have not yetparticipated in network communications). During the registration period232, new HNMs 28 register with the master HNM 28, transmit a self-trainburst to adapt the Phy parameters, and if already calibrated, transmitsa registration burst. An HNM 28 that transmits a registration burstsexpects to receive from the master HNM 28, in a subsequent cycle startburst, a response that includes a new identity for the registering HNM28 and a position in the UBR transmission order in which to transmit UBRbursts.

[0109] During a given registration period 232, more than one HNM 28might attempt to register with the master HNM 28. Accordingly,collisions between HNMs 28 can occur. However, the number of HNMs 28participating in any given registration period 232 is typically few;thus, the likelihood of collisions on the home network 10 is generallylow. Also, colliding HNMs 28 that do not successfully register duringthe present registration period 232 retransmit the registration requestduring a subsequent registration period 232. Each HNM 28 independentlyand randomly determines the number of registration cycles to wait beforeretransmitting a registration request. This random and independentretransmission reduces the likelihood that the colliding HNMs 28 willcollide again. Further, each HNM 28 that successfully registers during agiven registration period 232 does not communicate during subsequentregistration periods (subsequent transmissions by successfullyregistering HNMs 28 occur during the time slot allocated to that HNM28).

[0110] During a registration period 232, the master HNM 28 receives theregistration bursts, if any, from new HNMs 28. During the CBR period 230immediately following the registration period 232, the master HNM 28responds to one of the registration bursts with a cycle start burst thatincludes a master management message within the data field 206 of thecycle start burst. The master management message indicates to theregistering HNM 28 where that HNM 28 appears in the transmission orderduring the CBR period 230 and, if required, the amount of bandwidth thathas been allocated to the HMN 28.

[0111] If the master HNM 28 receives more than one registration request,the master HNM 28 responds to only one of the registration requests, andthe other registering HNMs 28 retransmit during a subsequentregistration period as described above. The master HNM 28 identifies theHNM 28 to which the master is responding in the Phy header 204 of thecycle start burst.

[0112] When the registration period 232 times out, the master HNM 28transmits an ACK burst, marking the start of an ACK period 226 (orcycle). In one embodiment, the first ACK burst (i.e., ACK0) marks thestart of the ACK period 226. In another embodiment, the registrationstart burst marks the start of the ACK period 226. During the ACK period226, each HNM 28, starting with the master HNM 28, transmits an ACKcorresponding to the UBR bursts during the previous fairness cycle 224.

[0113] ACK bursts are used for UBR traffic. Each HNM 28 sends anacknowledge message (ACK) for each burst that the HNM 28 receives. Ifthe transmitting HNM 28 does not receive an acknowledgement from one ofthe destinations, it retransmits the packets. Using acknowledgmentmessages improves the performance of the home network 10 in cases ofnoise that corrupt some burst traffic. Each burst is an aggregation ofpackets destined for one or more destinations. If an ACK is not receivedfrom one or some of the destinations in the burst, the messagescorresponding to the unacknowledged packets are retransmitted.

[0114] After the ACK period 226, a gap can appear in the communicationson the coax backbone 20 when the master HNM 28 is still processing thelast ACK burst of the ACK period 226. Then, the master HNM 28 marks theend of the ACK cycle and the start of the next fairness cycle 224 bytransmitting a UBR burst. If the expected time for the start of the nexttransmission cycle 222 arrives, the master HNM 28 transits a cycle startburst.

[0115] FIGS. 8A-8B show an embodiment of a process by which the masterHNM 28 controls communication on the coax backbone 20. To mark thebeginning of a transmission cycle 222, the master HNM 28 sends (step240) a cycle start burst onto the backbone 20. The cycle start burst caninclude master management data, an identity of each HNM 28 that is goingto transmit a data burst during the upcoming CBR period 228, and atransmission order for the HNMs 28 to follow during the CBR period 228.The listed identities are of those HNMS 28 that have requested from themaster HNM 28 a guaranteed bandwidth. In one embodiment, the cycle startburst includes information regarding the HNMs 28 that are to transmit aUBR burst during the transmission cycle, such as a transmission order.In another embodiment, the cycle start burst also includes the CBRtransmission order information.

[0116] The master HNM 28 monitors (step 242) the backbone 20 for CBRbursts.

[0117] When the master HNM 28 determines that the CBR period 228 hasended, and if a previous ACK cycle 224 has ended, the master HNM 28issues (step 246) a UBR burst to start a new ACK cycle. The master HNM28 monitors (step 248) the backbone 20 for subsequent UBR bursts. Themaster HNM 28 maintains (step 250) a timer to determine when the presenttransmission cycle 222 is to end. When the timer indicates the end ofthe transmission cycle 222, the master HNM 28 starts the next CBR period228 by issuing (step 252) a cycle start burst. Before issuing the cyclestart burst, the master HNM 28 waits for any burst in progress tocomplete.

[0118] When the master HNM 28 determines (step 254) that the currentfairness cycle 224 has ended, the master HNM 28 transmits (step 256) aregistration start burst to initiate a registration period 232. (In oneembodiment, the master HNM 28 can skip one or more fairness cycles 224before initiating the registration period 232.) During the registrationperiod 232, the master HNM 28 receives (step 258) zero, one or moreregistration requests. The master HNM 28 replies (step 260) to oneregistration request during the next CBR period.

[0119] The master HNM 28 maintains (step 266) a timer to determine whenthe registration period ends. When the timer indicates the end of theregistration period, the master HNM 28 sends (step 268) an ACK burst tomark the start of the ACK cycle. During the ACK cycle, the master HNM 28determines (step 270) when the present transmission cycle ends andissues (step 272) a cycle start burst to start the next CBR period 228.In one embodiment, the master HNM 28 waits until the ACK cycle endsbefore sending the cycle start burst. Also during the ACK cycle, themaster HNM 28 monitors (step 274) the backbone 20 for ACKs from theother HNMs 28. Upon detecting completion of the ACK cycle, includingwaiting for an ACK for its own UBR burst (i.e., if the ACK was requestedin that UBR burst), the master HNM 28 issues (step 276) a UBR burst (afairness cycle start burst) to start a new fairness cycle or a cyclestart burst to start a new transmission cycle if the expected time tostart a new transmission cycle has arrived.

[0120]FIG. 9 shows an embodiment of a process by which each HNM 28 inthe home network, other than the master HNM 28, communicates over thecoax backbone 20. In step 280, the HNM 28 receives a cycle start burstand determines from the cycle start burst its positions in thetransmission orders for CBR and UBR and its allocated amount ofbandwidth. The cycle start burst operates to synchronize communicationsbetween the HNM 28 and the master HNM 28. The HNM 28 monitors (step 282)the backbone 20 for CBR bursts, and after waiting for its own allottedtime in the CBR transmission order, if any, transmits (step 284) a CBRburst. By monitoring the backbone 20 for CBR bursts, the HNM 28determines when the CBR period is over (each HNM 28 can determine thelist of HNMs 28 participating in the CBR period from the informationprovided by cycle start burst).

[0121] After the CBR period 228 ends, the HNM 28 determines (step 286)whether it can transmit a UBR burst. To be enabled to transmit a UBRburst, in one embodiment the HNM 28 requires (step 288) a grant from theHNM 28 that precedes it in the transmission order. After transmittingthe UBR burst, the grant passes (step 290) to the next HNM 28 in the UBRtransmission order. In another embodiment, the HNM 28 awaits its turn(step 288′) to transmit the UBR burst by monitoring the backbone 20 andcounting the number of UBR bursts that were transmitted since the startof the current fairness cycle 224.

[0122] In step 292, the HNM 28 detects an ACK burst (or in oneembodiment a registration start burst) on the backbone 20, marking thestart of an ACK cycle. The HNM 28 determines (step 294) when to transmitthe ACK based on its position in the transmission order. If the HNM 28has an ACK to transmit (depending upon whether it received a UBRrequesting an ACK during the previous fairness cycle), the HNM 28transmits the ACK; otherwise the HNM 28 transmits an empty (null) burst.The HNM 28 can make this determination by monitoring the backbone 20 forACK bursts or by waiting to receive a grant from the HNM 28 immediatelypreceding in the UBR transmission order.

[0123]FIG. 10 shows an embodiment of a process by which a new HNM 28becomes part of home network 10. Upon detecting (step 296) aregistration start burst, the new HNM 28 issues (step 298) a Self_TrainBurst (for calibrating its PHY) or a registration request. If the newHNM 28 does not receive a reply indicating that the master HNM 28 hasregistered the new HNM 28, the new HNM 28 transmits (step 298) anotherregistration request in a subsequent registration period. The new HNM 28continues to transmit registration requests during subsequentregistration periods until the new HNM 28 becomes registered. In oneembodiment, the new HNM 28 randomly selects how many registrationperiods to skip before retransmitting the registration request. Afterbecoming registered, the new HNM 28 transmits bursts during the UBRperiod as described above.

[0124] Referring back to FIG. 1, the home network includes a pluralityof local buses 35 each connected to the coax backbone 20 network by anHNM 28. One of the HNMs 28 is the master HNM 28, and the local bus 35that is connected to the master HNM 28 is the prime bus. If the same HNM28 connects multiple local buses 35 to the coax backbone 20, each localbus 35 is of a different type (e.g., 1394 , Ethernet, USB); if that HNM28 is the master HNM 28 of the home network 10, then each of such localbuses 35 is deemed to be the prime bus (of its particular type).

[0125]FIG. 11 shows one embodiment of the home network 10, in which thebackbone 20 connects four IEEE 1394 local buses through different HNMs28. In this embodiment, each HNM 28 shown operates as a 1394-to-coaxbackbone bridge between the backbone 20 and the 1394 local bus connectedto that HNM 28. Devices 33 that are connected to one of the 1394 busesare referred to as 1394 devices or nodes. Although the backbone 20appears as a ring, this is for purposes of showing that the HNMs 28 areconnected to the backbone 20, and not intended to show that the backbone20 operates as a ring network.

[0126] There are two embodiments of the 1394-to-coax bridge. In a firstembodiment, each bridge operates according to the IEEE 1394.1 standard.In a second embodiment, the bridge emulates the plurality of 1394 busesas a single bus so that nodes connected to these 1394 local buses cancommunicate with each other as though on the same 1394 bus (i.e., usingthe short haul 1394 protocol).

[0127] For the second embodiment, to achieve the appearance that all1394 devices in the home network are residing on the same 1394 shorthaul bus, modifications are made to the 1394a Phy and Link layers 102,104. In brief, the modifications include the following:

[0128] 1) at the Phy layer 102, modifications to the reset,initialization, and identification processes enable device (or node)discovery throughout the home network 10; and

[0129] 2) at the Link layer 104, the addition of routing tables (in oneembodiment, one table is for isochronous traffic, and another table isfor asynchronous traffic, in another embodiment, one routing tablehandles both traffic types.) and the forwarding of packets (incorporatedwithin bursts) to the coax backbone 20 enable delivery of such packetsto remote buses over the backbone 20.

[0130] The Link layer 104 uses the asynchronous routing table todetermine whether the destination identifier of an asynchronous packetis on a remote bus (other than the local bus from which the packetoriginates). If the destination is on a remote bus, the Link layer 104sends an ACK_pending packet to the originator of the packet (i.e. sourcenode) and forwards the asynchronous packet to the backbone 20. The HNM28 incorporates the asynchronous packet within a burst, which canincludes other packets targeted to other destinations. If thedestination is not on a remote bus, the Link layer 104 operates as astandard Link layer to process the asynchronous packet.

[0131] Asynchronous packets between devices on the same local bus 35remain local to that bus 35. The HNM 28 does not forward such packets tothe backbone 20. The HNM 28 routes asynchronous packets destined to aremote device according the asynchronous routing table that resides inthat HNM 28 and responds to the packet by sending an ACK_ending packetto the packet originator). The asynchronous routing table defines remoteHNMs 28 according to the Phy_ID in the asynchronous packet destinationfield. The HNM 28 forwards isochronous channel packets and asynchronousstreams through the backbone 20 to all the other buses or to other busesaccording to the isochronous routing table. One clock reference existsfor the home network 10. The prime bus generates the common clock, whichthe HNMs 28 connected to at the other buses each recover.

[0132] Referring again to FIG. 11, each local 1394 bus has the followingfeatures. Each 1394 node receives a unique Phy identification number(Phy_ID) (0-62), and each HNM 28 receives the same Phy_ID number (anumber that is unique from those assigned to the nodes). For each localbus 35, the bus identification number (Bus_ID) is equal to 0×3FF. Thehome network 10 has one Isochronous Resource Manager (IRM), which is oneof the HNMs 28, typically the master HNM 28. Each isochronous channeland each asynchronous stream that is generated in the home network 10receives its channel number and bandwidth allocation from the singleIRM. Each local 1394 bus 35 has its own Cycle Master, which is the HNM28 of that bus. Each local bus 35 has its own Bus Manager. Arbitration,signaling and data transfers are local to each local bus 35.

[0133] Each HNM 28 performs various operations to cause the other remotebuses to appear as though on its local bus. Such operations include:

[0134] 1) sending self-identification (Self_ID) packets according to areset procedure used for discovering 1394 nodes;

[0135] 2) forwarding streams through the backbone 20, with updatingtimestamp of 61883 isochronous packets (the 61883 is a standard thatspecifies transport of MPEG signals over the 1394 and allows the videotransfers between 1394 devices);

[0136] 3) sending acknowledge pending (ACK_pending) packets to thesource of asynchronous packets that are to be delivered to other remotebuses according to the asynchronous routing table (responding with anACK_pending packet satisfies a 10 uSec requirement for ACKs in standard1394 communications, although an acknowledgement issued by the target ofthe packets can experience a latency over the backbone 20 of greaterthan 10 uSec);

[0137] 4) forwarding asynchronous packets that are to be delivered toother remote buses through the backbone 20 according to the asynchronousrouting table;

[0138] 5) receiving asynchronous packets over the backbone 20 from otherremote buses targeted to a device on the local bus of the HNM 28; and

[0139] 6) distributing a reset that occurs on one bus to the otherbuses.

[0140] To initialize the home network 10, the HNMs 28 perform a globalreset process. During the global reset process, the home network 10conducts an initialization and identification process. As a result, anemulated bus structure is created where all 1394 devices in the network10 see each other, and each 1394 device has a unique Phy_ID. After theend of initialization and identification processes, each HNM 28 appearsas a root 1394 node with three Phy ports.

[0141]FIG. 12 is an embodiment of the emulated bus structure from theperspective of each of the HNMs 28. Each HNM (HNM1, HNM2, HNM3, HNM4) isa root node for its respective local bus. Port 1 (P1) of each HNM 28 isconnected to the local bus. Phy port 0 (P0) and Phy port 2 (P2) appearto all 1394 devices on the local bus either as not connected or as abranch of the bus. The branch appears to contain other 1394 devices thatare physically located in other buses but logically appear to the localbus devices as if they are reside on the same bus. For example, for HNM1, the P0 port appears as unconnected, the P1 port is connected to thephysical bus of HNM1, and the P2 port is an emulation of the other localbuses in the home network 10, namely, remote buses of HNM 2, HNM 3, andHNM 4. As another example, for HNM 2, the P0 port is an emulation of theremote bus of HNM 1, the P1 port is connected to the physical bus ofHNM2, and the P2 port is an emulation of the remote buses of HNM 3, andHNM 4. Thus, all existing 1394 devices in the network seemingly resideon the same bus. Therefore, any application that works with 1394 busesis supported over the entire home network 10.

[0142] Each HNM 28 generates two types of self-ID packets: 1) HNM 28self ID_packets, and 2) emulated self-ID packets. HNM self-ID packetsissued by each HNM 28 describe the three-port root node (shown in FIG.12) for that HNM 28. Emulated self-ID packets describe all nodes on theother HNM local buses. Each emulated self-ID packet represents the busstructure of two port nodes (P0 and P2) that are connected serially tothe root node as one branch.

[0143] Initialization of the home network 10 occurs after the backbone20 has been initialized, that is, the number (N) of HNMs 28 is known,each HNM 28 has its own number (1 through N), and a master HNM 28 isselected. When the initialization ends, the home network 10 isoperational.

[0144] Referring to FIG. 13, during initialization, the master HNM 28sends (step 304) through the backbone 20 a first global reset packet toall the HNMs 28. The reset is performed (step 308) in each bus with theroot (i.e., the appropriate HNM 28) governing the reset process. Afterthe reset, each HNM 28 sends (step 312) an updating bus message to themaster HNM 28. The updating bus message includes: 1) the Phy_JD of theHNM 28 (i.e., the number of nodes on the bus -1); 2) the link state(active/not active) for each node on the local bus, and 3) an indicatorfor each node on the local bus whether that node is “bridge capable.” (A“bridge capable” device is a 1394 device that is compliant with the IEEE1394.1 standard.) Also, after the reset, each bus functions locally.

[0145] From the updating bus messages obtained from the HNMs 28, themaster HNM 28 generates (step 316) a network table. For each HNM 28, thenetwork table includes the number of nodes in the local bus of that HNM28, the link status (active/inactive) of each node in the local bus ofthat HNM 28, and the bridge capabilities for each node in the local busof that HNM to 28. After producing the network table, the master HNM 28transmits (step 320) the network table to each HNM 28 using anupdate_network_table message. The update_network_message includes thetime for generating the next bus reset. Each HNM 28 updates (step 324)its own network table accordingly.

[0146] At the time specified in the update_network_table message, eachHNM 28 generates (step 328) a bus reset. After the network completes theinitialization, the home network undergoes a network update process. Instep 332, if there are no topology changes in the local bus, the resetis not propagated to other buses. After the local bus reset sequence iscompleted and the HNM 28 port obtains its new Phy_ID, this informationis propagated (step 334) by a new_phy_id message to the master HNM 28.The master HNM 28 updates (step 336) the network table and sends (step340) a update_network_table message to the other HNMs 28. Upon receivingthe update_network_table message, each HNM 28 proceeds as describedabove, that is, by locally resetting the bus (step 308), updating thenetwork table (step 324), and emulating the home network 10 in that bus.

[0147] After the completion of the initialization of the home network,each HNM 28 handles asynchronous packets received from the bus(inbound—upstream from local bus to backbone) and asynchronous packetsreceived from the backbone 20 (outbound—downstream from backbone to thelocal bus). Although described in terms of local 1394 buses, theprinciples of packet handling applies also to other bus types, such asUSB, Ethernet, etc.

[0148]FIG. 14 shows an embodiment of a process for use by each HNM 28when handling inbound asynchronous packets. For inbound asynchronouspackets, each HNM 28 forwards such packets to the backbone 20 based onthe physical ID (Phy ID) destination address, the physical ID of the HNM28, and the network table. During the initialization process, each HNM28 maintains two registers, one with the Phy_ID of the node with thelowest ID on its local bus and one with the highest ID on the local bus.A Phy_ID between the highest and lowest IDs is on the local bus.

[0149] In step 354, If the bus ID is equal to 0×3FF, which identifiesthe local bus as a 1394a bus, the HNM 28 performs the following actions:

[0150] 1. In step 358, if the Phy_ID is equal to 0×3F16, this indicatesthat the packet is a broadcast packet. In step 362, if the HNM 28 is themaster HNM 28, then the HNM 28 forwards (step 366) and processes (step370) the packet. If the HNM 28 is not the master HNM 28, then the HNM 28forwards (step 374) the packet. In this instance, the non-master HNM 28does not process the broadcast packet, thus preventing broadcast packetsfrom accessing non-master HNMs 28. Access to non-master HNMs 28 is theprivilege of master HNMs 28, not devices on the local bus.

[0151] 2. In step 378, if the Phy_ID does not correspond to a node onthe local bus, the HNM 28 forwards (step 382) the packet to the backbone20 and issues (step 386) an ACK_pending (busy or retry) packet to thelocal bus.

[0152] 3. In step 390, if the Phy_ID corresponds to a node on the localbus (but not the Phy_ID of the HNM 28), the HNM 28 discards (step 392)the packet.

[0153] 4. In step 398, if the Phy_ID is that of the HNM 28, the HNM 28processes (step 394) the packet if the HNM 28 is the master HNM 28, andforwards (step 396) the packet if the HNM 28 is not the master HNM 28.Again, access to non-master HNMs 28 is the privilege of master HNMs 28,not devices on the local bus.

[0154] If the bus ID does not equal 0×3FF, the HNM 28 forwards (step398) the packet and issues an ACK_pending packet to the local bus.

[0155]FIG. 15 shows an embodiment of a process for use by each HNM 28when handling outbound asynchronous packets. For outbound asynchronouspackets, each HNM 28 forwards such packets from the backbone 20 to thelocal bus 35 based on the physical ID destination address, the physicalID of the HNM 28, and the network table. If addressed to the address ofthe HNM 28, a packet passes to the HNM 28 only if the source of thatpacket is the master HNM 28 (a flag in the packet can indicate that thesource of the packet is the master HNM 28).

[0156] In step 404, if the bus ID is equal to 0×3FF, the HNM 28 performsthe following actions:

[0157] 1. In step 408, if the Phy_ID is equal to 0×3F16, this indicatesthat the packet is a broadcast packet; if so, the HNM 28 forwards (step412) the packet to the local bus.

[0158] 2. In step 416, if the Phy_ID does not correspond to a node onthe local bus, the HNM 28 discards (step 420) the packet.

[0159] 3. In step 424, if the Phy_ID corresponds to a node on the localbus (but not the Phy_ID of the HNM 28), the HNM 28 forwards (step 428)the packet to the local bus.

[0160] 4. In step 432, if the Phy_ID is that of the HNM 28, the HNM 28processes (step 436) the packet if the HNM 28 is the master HNM 28, anddiscards (step 440) the packet if the HNM 28 is not the master HNM 28.

[0161] If the bus ID does not equal 0×3FF, the HNM 28 forwards (step444) the packet to the local bus.

[0162] For isochronous streams, in one embodiment, each HNM 28 forwardsto the local bus 35 those streams that are received from the backbone 20and forwards to the backbone 20 those streams that are received from thelocal bus 35. The HNMs 28 forward the packets in these streams as thepackets are received; that is, the HNMs 28 do not need to filter thesepackets.

[0163]FIG. 16 shows another embodiment of the DPU 14′ including a firstsplitter-combiner 460, which receives signals from and transmits signalsto the cable television/internet network 18. The splitter-combiner 460distributes those signals to the components of the DPU 14′ from thecable television/internet network 18 and collects signals from thecomponents of the DPU 14′ for transmission to the cabletelevision/internet network 18. Similarly a second splitter-combiner 464receives signals from and transmits signals to the various rooms 30through the coax cables 22. The splitter-combiner 464 distributessignals received from the various rooms 30 to the components of the DPU14′ and distributes signals from the components of the DPU 14′ to thevarious rooms 30. The embodiment shown in FIG. 11 uses the frequencyband of 5-45 Mhz for the home network signal, and the frequency band50-850 MHz for the cable TV and Internet provider signals.

[0164] The components of the DPU 14′ can be modified to achieve theother frequency bands described above for carrying the home networksignal.

[0165] The components of this embodiment of the DPU 14′ include ahigh-pass filter 470 connected between the first splitter combiner 460and the second splitter combiner 464. The high-pass filter 470 allowsthe transparent connection of legacy TV cable network in the forward andreverse channels, while blocking the specific frequency channels thatare allocated for the internal home network signal. In one embodiment,this high-pass filter 470 has a cut-off frequency of 50 MHz, thuspermitting signals having a frequency greater than the 50 MHz high-passcut-off to pass transparently between the splitter-combiners 460, 464.Signals above this frequency are typically legacy television signals(i.e., 55-850 MHz) and therefore should pass unimpeded through the DPU14′. Frequencies lower than the cut-off are thus available for use bythe home network signal.

[0166] The DPU 14′ is responsible for allowing the RDC OOB and RDC CMsignals to pass from the set top boxes and cable modems, respectively,to the head-end of the cable television network 18. To accomplish this,the DPU 14′ includes a Forward OOB receiver and decoder 490 and a cablemodem 474. The cable modem 474 and Forward OOB receiver 490 receive thedata from the OOB Forward Data Channel and decode the signal to acquireinformation concerning which frequency is to be used as the RDC OOB andRDC CM channels. A controller 492 receives the OOB information, extractsthe information on the current frequency bands that are being used inthe home, and directs the home network 10 to use other frequency bands.After this frequency information is obtained, the DPU 14′ controls thehome network 10 so that no signals are transmitted on this OOB RDC andRDC CM frequency. A notch filter achieves this control, in oneembodiment, by blocking passage of signals within the RDC OOB and RDC CMfrequency region. In another embodiment, the corresponding tones of themulti-carrier signals are silenced. A regular multi-tone transmitter(either OFDM or DMT) determines whether to transmit power on eachparticular tone. Each tone can be silenced according to a managementmessage from the controller 492. The controller 492 in the DPU 14′distributes this management message to each of the HNMs 28 identifyingthe tones that are to be silenced.

[0167] When a device 33 in the home needs to transmit data back to thehead-end using the OOB RDC or RDC CM channel, the RDC signal isintercepted by the DPU 14′ and transmitted to the cable televisionnetwork 18. This is accomplished using an OOB regenerator(receiver/transmitter) 486. Signals received from the home devices 33are down-converted and demodulated, then modulated and up-converted tothe required transmitted frequency, and then transmitted to the cabletelevision/internet network 18.

[0168] The cable modem (CM) 474 provides Internet access to the home.Other types of access modems are also available if the Internet accessis provided on another media than the Cable networks (e.g. a DSL modemcan be used if Internet access is provided on the telephone linenetwork). For example, a digital subscriber line (DSL) modem replacesthe cable modem 474 if a telephone network is providing Internet access.In such an embodiment, connection between the DPU 14′ and the Internet18 is not through the splitter-combiner 460, but instead is throughanother connector such as a RJ11 connector. An alternative embodimentincludes the functionality of the cable modem in a set-top box locatedin the home (in which case, the cable modem 474 is not part of the DPU14′). In yet another embodiment, the cable modem 474 is a standalonedevice (not in a set top box or in the DPU 14′. In this case, the cablemodem 474 is connected to the backbone 20 through a HNM 28

[0169] In addition, the cable modem 474 is connected to a hub/router 478for transmitting data to and from the Internet 18. The hub/router 478(or bridge) provides hub and routing functionality that distributes theexternally generated data signals (Internet) and the home network signalto the HNMs 28 in the home. The hub (or bridge) and routingfunctionality can be based on an interface such as 100-Base-T Ethernet,IEEE -1394, or USB. The signals from each output port of the hub/routerare quadrature amplitude modulated (QAM) to produce QAM signals, with aprogrammable constellation size, over a pre-defined frequency range. Asan example, with a 256-QAM modulation and a symbol rate of up to 40 MHz,the available throughput can reach up to 320 Mbps. A capability to notchfilter the signal at programmable frequencies is also provided.

[0170] The QAM signal in various embodiments is either a single carrierQAM, or multi-band QAM, which is a summation of several QAM signals withdifferent carrier frequencies. In another embodiment, the signal ismodulated as a multi-carrier signal with approximately the sameavailable throughput. The output-modulated signals are combined with theexternal cable TV signal stream and transmitted over the backbone 20 tothe various rooms 30. A Media Access Controller (MAC) 482, 482′(generally 482), located between the hub/router functionality and theQAM or multi-tone modulators provides the functionality that allows theco-existence of several data sources over the same cable (networking),e.g. arbitration, signal detection, etc.

[0171] While the invention has been shown and described with referenceto specific preferred embodiments, it should be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the invention asdefined by the following claims.

What is claimed is:
 1. A home network, comprising: a network backbone; aplurality of modules connected to the network backbone, each modulebeing connected between the network backbone and a local bus; and ademarcation point unit receiving a home network signal from one of themodules over the network backbone and passing the home network signal tothe plurality of modules.
 2. The home network of claim 1 wherein thenetwork backbone includes a plurality of coaxial cables.
 3. The homenetwork of claim 2 wherein the coax cables are part of pre-existingcable equipment installed in a home in which the home network resides.4. The home network of claim 1 wherein the network backbone includes atleast one splitter.
 5. The home network of claim 1 wherein one module isin communication with a plurality of local buses.
 6. The home network ofclaim 5 wherein one of the local buses is a 1394 local bus and anotherof the local buses is one of a universal serial bus (USB), Ethernet bus,and a Internet Protocol (IP) bus.
 7. The home network of claim 5 whereinat least two of the modules are in communication with 1394 local buses.8. The home network of claim 5 wherein at least two of the modules arein communication with USB local buses.
 9. The home network of claim 5wherein at least two of the modules are in communication with Ethernetlocal buses.
 10. The home network of claim 1 wherein the demarcationpoint unit is connected to an external network, the demarcation pointunit receiving an external signal from the external network and passingthe CaTV and the home network signals together over the networkbackbone.
 11. The home network of claim 10, wherein the external signalis a cable TV (CaTV) signal.
 12. The home network of claim 10, whereinthe external signal is a satellite signal.
 13. The home network of claim10 further comprising an electronic device connected to the demarcationpoint unit to receive the external signal.
 14. The home network of claim10, wherein at least one of the modules is integrated into a cable TVdevice.
 15. The home network of claim 14, wherein the cable TV device isa cable modem and the external signal is a cable modem signal.
 16. Thehome network of claim 15, wherein the cable TV device is a set top box.17. The home network of claim 10 wherein at least one of the modules isintegrated into a computer.
 18. The home network of claim 11, wherein afrequency of the home network signal is above a frequency of theexternal signal.
 19. The home network of claim 18, wherein the frequencyis of the home network signal is higher than approximately 2100 MHz. 20.The home network of claim 18, wherein the frequency is of the homenetwork signal is less than approximately 1050 MHz.
 21. The home networkof claim 20, wherein the network backbone includes a splitter having anoperational range of less than 900 MHz.
 22. The home network of claim 1,wherein the demarcation point unit includes a signal reflector unit thatreceives the home network signal having a first frequency and passes tothe plurality of modules the home network signal having a secondfrequency.
 23. The home network of claim 22, wherein the first frequencyis the same as the second frequency.
 24. The home network of claim 22wherein the second frequency is different than the first frequency. 25.The home network of claim 1, wherein the network backbone conveyscommunications between the modules at approximately 100 Mbps.
 26. A homenetwork comprising: a demarcation point unit receiving a signal from anetwork that is external to the home; a plurality of modules eachconnected to the demarcation point unit by one or more coax cables andto a device by a local bus, one of the modules receiving a message fromthe device connected to that one module by the corresponding local busand transmitting the message to the demarcation point unit; wherein thedemarcation point unit receives the message from that one module andtransmits the message and the signal together to each of the pluralityof modules over the coax cables.
 27. A demarcation point unit connectedbetween a home network backbone and an external network, the demarcationpoint unit comprising: a diplexer receiving a home network signal fromthe home network backbone and an external signal from the externalnetwork, the diplexer separating the home network signal from theexternal signal; and a signal reflector unit receiving the home networksignal from the diplexer and returning the home network signal back tothe home network backbone.
 28. The demarcation point unit of claim 27wherein the signal reflector unit is an output of the diplexer thatreflects the home network signal back to the home network backbone. 29.The demarcation point unit of claim 28 wherein the output of thediplexer is shorted to ground.
 30. The demarcation point unit of claim28 wherein the output of the diplexer is unterminated.
 31. Thedemarcation point unit of claim 27 wherein the signal reflector unitincludes a given coax cable connected to an output of the diplexer, thegiven coax cable reflecting the home network signal back to the homenetwork backbone.
 32. The demarcation point unit of claim 28 wherein oneend of the given coax cable is shorted to ground.
 33. The demarcationpoint unit of claim 25 wherein one end of the given coax cable isunterminated.
 34. The demarcation point unit of claim 27 wherein thesignal reflector unit includes a delay line in communication with thediplexer.
 35. The demarcation point unit of claim 34 wherein one end ofthe delay line of the signal reflector unit is shorted to ground. 36.The demarcation point unit of claim 34 wherein one end of the delay lineof the signal reflector unit is unterminated.
 37. The demarcation pointunit of claim 27 wherein the signal converter unit includes a RFconverter that changes a frequency of the home network signal before thehome network signal returns to the home network backbone.
 38. Thedemarcation point unit of claim 37 wherein the home network signalpassing to the diplexer from the home network backbone is an upstreamsignal, the home network signal returning to the home network backbonefrom the signal reflector unit is a downstream signal, and the diplexeris a first diplexer, and wherein the signal reflector unit includes asecond diplexer having an input/output (I/O) in communication with thefirst diplexer and an input in communication with the RF converter, thesecond diplexer separating the upstream signal received by the I/O fromthe downstream signal received by the input.
 39. The demarcation pointunit of claim 38 wherein the second diplexer returns the downstreamsignal to the first diplexer over the I/O.
 40. The demarcation pointunit of claim 38 further comprising an output in communication with theRF converter, and wherein the second diplexer passes the upstream signalto the RF converter over the output.
 41. The demarcation point unit ofclaim 37 wherein the RF converter includes a RF down-converter incommunication with a RF up-converter, the RF down-converter changing thefrequency of the upstream signal to an intermediate frequency and the RFup-converter changing the intermediate frequency to the frequency of thedownstream signal.
 42. The demarcation point unit of claim 38 whereinthe frequency of the upstream signal is higher than the frequency of thehome network signal.
 43. The demarcation point unit of claim 38 whereina power level of the upstream signal received at the signal reflectorunit is constant.
 44. The demarcation point unit of claim 38 wherein apower level of the downstream signal leaving the signal reflector unitis constant.
 45. The demarcation point unit of claim 38 wherein homenetwork signal passing to the diplexer from the home network backbone isan upstream signal, and the home network signal returning to thediplexer from the signal reflector unit is a downstream signal, andfurther comprising a splitter connected between the diplexer and thehome network backbone, the splitter receiving the downstream signal fromthe diplexer and passing the returned downstream signal to the homenetwork backbone over a plurality of coax cables.
 46. The demarcationpoint unit of claim 45 wherein the splitter receives the upstream signalfrom the home network backbone for transmission to the diplexer.
 47. Thedemarcation point unit of claim 27, wherein the diplexer combines thehome network signal received from the signal reflector unit with theexternal signal received from the external network and transmits thecombined signal to the home network backbone.
 48. A network moduleconnected between a network backbone and a local bus, comprising: adiplexer receiving from the network backbone an analog signal andseparating a home network signal from the analog signal; a modemconverting the home network signal to a digital signal; a media accesscontroller (MAC) controlling communications of the network module withother modules connected to the network backbone; and a switching fabricinterfacing with a protocol of the local bus to deliver the digitalsignal to the local bus.
 49. The home network module of claim 48,further comprising a transmission power controller controlling a powerlevel of the home network signal.
 50. In a home network having aplurality of network modules connected to a coax backbone, a method forcommunicating over the coax backbone between network modules, the methodcomprising; transmitting a cycle start burst over the backbone to starta transmission cycle during which the network modules transmit burstsover the backbone; allocating a first portion of the transmission cyclefor the transmission of isochronous bursts by the network modules; andallocating a second portion the transmission cycle for the transmissionof asynchronous bursts by the network modules.
 51. The method of claim50 further comprising establishing a transmission order for the networkmodules to follow when transmitting isochronous bursts over thebackbone.
 52. The method of claim 51 wherein the cycle start burstincludes the transmission order.
 53. The method of claim 50 furthercomprising establishing a transmission order for the network modules tofollow when transmitting asynchronous bursts over the backbone.
 54. Themethod of claim 53 wherein the cycle start burst includes thetransmission order.
 55. The method of claim 50 further comprisingdetermining that the transmission cycle has ended and allowingtransmission of an asynchronous burst to complete after the end of thetransmission cycle.
 56. The method of claim 50 further comprisingdetermining those network modules that are requesting bandwidth fortransmitting isochronous bursts.
 57. The method of claim 50 furthercomprising designating one of the modules to be a master network module,and wherein the master module transmits the cycle start burst.
 58. Themethod of claim 50 further comprising synchronizing the network modulesto the cycle start burst.
 59. The method of claim 50 further comprisingtransmitting a registration start burst.
 60. The method of claim 50further comprising allocating bandwidth in the first portion of thetransmission cycle to each network module requesting a guaranteedquality of service.
 61. The method of claim 50 further comprisingmonitoring, by a given network module, asynchronous bursts on thebackbone to determine when the given network module can transmit anasynchronous burst.
 62. The method of claim 50 further comprisingreceiving, by a given network module, a grant signal over the backboneto indicate that the given network module can transmit an asynchronousburst.
 63. The method of claim 50 further comprising monitoring, by agiven network module, isochronous bursts on the backbone to determinewhen that network module can transmit an isochronous burst.
 64. Themethod of claim 50 further comprising transmitting, by a given networkmodule, an empty burst if the given network module has no data totransmit during the second portion of the transmission cycle.
 65. Themethod of claim 50 further comprising transmitting, by a given networkmodule, a self-train burst.
 66. In a home network having a plurality of1394 buses each connected to a network backbone by a network module, thenetwork backbone including a plurality of coax cables, each networkmodule providing a bridge between the network backbone and the 1394 busconnected to that network module, the bridge comprising: a 1394 Phylayer; and a 1394.1 link layer routing communications among theplurality of 1394 buses over the coax cables of the network backbone.67. The bridge of claim 66 wherein the 1394 Phy layer is modified toenable an emulation of the plurality of 1394 buses in the home networkas a single 1394 bus.
 68. In a home network having a plurality ofnetwork modules connected to a network backbone, the network modulescommunicating with each other over the network backbone using burstshaving a plurality of burst types, a burst comprising: a preamblesignifying a start of the burst and the type of the burst; a headerproviding at least one parameter for decoding the burst; and a dataportion carrying QAM (quadrature amplitude modulation) symbol data. 69.The burst of claim 68 wherein the preamble includes a periodic preambleportion having a length, the length of the periodic preamble determiningthe type of the burst.
 70. The burst of claim 68 wherein the preambleincludes a periodic preamble portion having symbols that periodicallyalternate in sign, wherein the alternating symbols determine the type ofthe burst.